Al-Kāfi
Hadith 23334ـ عَنْهُ عَنْ مُحَمَّدِ بْنِ عَلِيٍّ عَنِ النَّضْرِ بْنِ شُعَيْبٍ عَنْ أَبَانِ بْنِ عُثْمَانَ عَنِ الْحَسَنِ بْنِ السَّرِيِّ عَنْ أَبِي عَبْدِ الله (عَلَيهِ السَّلام) قَالَ لا تَكْتُبْ دَاخِلَ الْكِتَابِ لأبِي فُلانٍ وَاكْتُبْ إِلَى أَبِي فُلانٍ وَاكْتُبْ عَلَى الْعُنْوَانِ لأبِي فُلانٍ.
4. It is narrated from him (narrator of the Hadith above) from Muhammad ibn Ali from al-Nadr ibn Shu’ayb from Aban ibn ‘Uthman from al-Hassan ibn al-Sari from Abu ‘Abdillah (a.s.) who has said the following: “Do not write in the letter: ‘For abu so and so’ but write ‘To abu so and so’. In the address area one should write, ‘For abu so and so’.”